1. Field of the Invention
The present invention relates generally to communication systems, and more particularly to receivers for use in spread spectrum communication systems.
2. Related Art
In the past, direct-sequence spread-spectrum techniques have not been widely used due to their relatively high cost. However, the recent development and use of custom digital VLSI (very large scale integration) techniques have made the cost of spread-spectrum signal processing affordable. Consequently, direct-sequence spread-spectrum techniques have received much attention in the last few years as a viable technological option for many commercial applications, such as for commercial portable mobile communication systems.
Conventionally, spread-spectrum transceiver components are implemented in an economic manner using application-specific integrated circuit (ASIC) chips. The use of ASIC chips in spread spectrum transceiver components has heretofore been deemed necessary due to the rather unique signal processing requirements associated with spread spectrum communication. In particular, in a spread-spectrum receiver, the design philosophy is to tolerate interference. Designing to tolerate interference results in a higher quality radio, and can lead to an increase in the network capacity. As will be appreciated, such design philosophy associated with spread-spectrum receivers generally differs from the design philosophy employed when developing conventional narrowband radios.
As a result of the rather unique signal processing requirements associated with spread spectrum communication, in the past it has not been possible to employ standard digital signal processing techniques when developing spread-spectrum receivers. This represents a disadvantage of conventional spread-spectrum receivers, since digital signal processing techniques offer the ability to employ powerful signal conditioning and processing algorithms that give rise to robust receivers. Consequently, generic, general purpose spread spectrum digital signal processors (DSP) do not currently exist.